Hi maddys52
Just a bit puzzled as as to why you've altered Beg's quote and added the names "Ruby May HODGES". 
Mea culpa :-)
I too read Maddy's reply and wondered why the names were wrong. Checked the reply that she had quoted and saw that I had written the wrong name. Proof positive, if needed, that there's no cure for stupid...
I amended my original reply but obviously couldn't do the same to Maddy's quoted reply.
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There's really only two births
that I could find in Southland which match the 21 Nov 1891 birthdate, don't appear later in BDM NZ Marriages and don't have younger siblings.
1891/16420 - HOWARD, Bridget - mother: Elizabeth father: Thomas
1891/16244 - LUSCOMBE, Clarice Francis - mother: Frances father: Edwin
Neither of the mother's maiden names, DOOGAN and LAWRENCE respectively, have popped up previously but I'll mention them.
I'm thinking either 21 Nov 1891 is the wrong birthdate or the birth went unregistered.
Ruby not being their natural daughter is an obvious possibility but short of words to that effect in their divorce file, or an mtDNA test, I can't think of a way to prove/disprove it.
Regards
Beg